Organophosphorus (OPs) compound are potent neurotoxic chemicals that are widely used in medicine, industry and agriculture; most notably as insecticides. The neurotoxicity which is primarily a result of AChE inhibition, may take the form of cholinergic crisis and death as a consequence of acute exposure or psychiatric symptoms and delayed neuropathy following chronic exposure. Usually, treatment of insecticide poisoning consists of supportive care and specific therapy e.g. atropine and oximes, which often fail to prevent morbidity or death. Currently, recombinant (r) BChE is a leading pre-exposure treatment candidate for OP toxicity due to its potent bioscavenging ability but because of its 1:1 stoichiometry with OP, large doses will be required if delivered by i.m. or subcutaneously routes. In order to reduce the dose required for systemic approaches for delivering BChE, we plan to create a protective BChE bioshield of aerosolized tetrameric rBChE into the lungs to detoxify incoming (inhaled) OPs in situ, thus preventing the OP's entry into the systemic circulation and avoiding the respiratoty usually associated with inhalation exposure. Phase I represents a feasibility study in mice to examine (i) the patterns of deposition of either liquid or powdered PEG-rMaBChE radioaerasols delivered to the lungs by Microsprayer or insufflator respectively (ii) the persistence of the bioshield and (iii) the degree of protection it affords against 50% LD50 of the liquid aerosolized OP insecticide paraoxon as measured by percent inhibition of RBC AChE and serum BChE. In Phase II, the efficacy of the aerosolized PEG-rMaBChE to protect against OP toxicity will be tested in a homologous macaque model. A homologous system, which does not make anti-BChE antibodies, is critical for accurate efficacy, pharmacokinetics and safety testing of a recombinant therapeutic protein which may be required as a multiple administrations. During this time, Master and Working Cell Banks of CHO-K1 producing rHuBChE will be generated and process development begun on the production, purification and PEG-ylation protocols. The efficacy of an aerasolized PEG-rHuBChE bioshield to prevent paraoxon toxicity will be tested in macaques and compared with the homologous rMaBChE enzyme. It is anticipated that aerosol delivery will reduce the dose required for protection because of its concentration in the same areas as the inhaled insecticide. The development of an innovative Microsprayer type device would permit a user friendly treatment to be delivered before the known use/release of insecticides. Public Health Relevance: Many glycoproteins which are potent antidotes, exhibit very important physiological functions but cannot be used as therapeutic treatments because they are quickly removed from the circulation or their ability to protect requires large doses if given i.m. The aim of this project is to butyrylcholinesterase as an aerosol in a pulmonary delivery device to that it deposits in the lung and forms a bioshield and detoxifies inhaled indecticides poisons in the lung and prevernts them from reaching the blood and the neuromuscular junctions where they can quickly cause severe toxicity.